Hydrochemical research

To carry out the determination of hydrogen sulfide, a special laboratory was deployed in the village of Bakirovo, mainly organized by the laboratory of biological chemistry of the Medical Research Institute [1] with the full assistance of TNKZdrav.

Quantification of Hydroperoxides by Gas Chromatography with Flame Ionisation Detection

Hydroperoxides are of great importance in the fields of atmospheric and biological chemistry. However, there are several analytical challenges in their analysis: unknown and usually low UV absorption coefficients, high reactivity, thermal instability, and a lack of available reference standards. To overcome these limitations, we propose a GC-FID approach involving pre-column silylation and quantification via the effective carbon number approach. Four hydroperoxides of α-pinene were synthesized in the liquid phase with singlet oxygen and identified using literature data on isomer yield distribution, MS spectra, estimated boiling temperatures of each isomer (retention time), their thermal stability and derivatisation rate. The developed procedure was used for the determination of hydroperoxides in bottled and autooxidised turpentine. We anticipate that this method could also be applied in atmospheric chemistry, where the reactivity of singlet oxygen could help explain the high formation rates of secondary organic aerosols.

Biological Mechanisms of S-Nitrosothiol Formation and Degradation: How Is Specificity of S-Nitrosylation Achieved?

The modification of protein cysteine residues underlies some of the diverse biological functions of nitric oxide (NO) in physiology and disease. The formation of stable nitrosothiols occurs under biologically relevant conditions and time scales. However, the factors that determine the selective nature of this modification remain poorly understood, making it difficult to predict thiol targets and thus construct informatics networks. In this review, the biological chemistry of NO will be considered within the context of nitrosothiol formation and degradation whilst considering how specificity is achieved in this important post-translational modification. Since nitrosothiol formation requires a formal one-electron oxidation, a classification of reaction mechanisms is proposed regarding which species undergoes electron abstraction: NO, thiol or S-NO radical intermediate. Relevant kinetic, thermodynamic and mechanistic considerations will be examined and the impact of sources of NO and the chemical nature of potential reaction targets is also discussed.

Introducing integrated language skills assessment at the language department of a Czech university

Integrated assessment evaluates language proficiency through tasks that require the test-taker to produce a written or spoken output based on listening or reading comprehension (reading or listening-into-writing or speaking). Since integrated assessment aims at reflecting the communicative and cognitive requirements of academic life and other professions, it is considered a means of assessment that is both authentic and valid. Examples of integrated tests can be found in high-stakes examinations at universities with English as the medium of instruction, and in the standardised high-stakes examinations offered by ETS, Pearson Education and Trinity College London. This report provides an example of integrated assessment in action by describing a currently used integrated test developed at the Language Department of the Faculty of Science, University of South Bohemia in the Czech Republic. Since 2018, this particular integrated test has served as the entrance examination for Biological Chemistry (EEBC), a bachelor’s degree course delivered entirely in English. By detailing the rationale behind the examination and the design process, this report aims to show that integrated assessment can provide a valid alternative to independent assessment at the tertiary level.

Diversification of 4ʹ-Methylated Nucleosides by Nucleoside Phosphorylases

The growing demand for 4'-modified nucleoside analogs in medicinal and biological chemistry is contrasted by the challenging synthetic access to these molecules and the lack of efficient diversification strategies. Herein, we report the development of a biocatalytic diversification approach based on nucleoside phosphorylases, which allows the straightforward installation of a variety of pyrimidine and purine nucleobases on a 4'-alkylated sugar scaffold. Following the identification of a suitable biocatalyst as well as its characterization with kinetic experiments and docking studies, we systematically explored the equilibrium thermodynamics of this reaction system to enable rational yield prediction in transglycosylation reactions via principles of thermodynamic control.<br>

Diversification of 4ʹ-Methylated Nucleosides by Nucleoside Phosphorylases

The growing demand for 4'-modified nucleoside analogs in medicinal and biological chemistry is contrasted by the challenging synthetic access to these molecules and the lack of efficient diversification strategies. Herein, we report the development of a biocatalytic diversification approach based on nucleoside phosphorylases, which allows the straightforward installation of a variety of pyrimidine and purine nucleobases on a 4'-alkylated sugar scaffold. Following the identification of a suitable biocatalyst as well as its characterization with kinetic experiments and docking studies, we systematically explored the equilibrium thermodynamics of this reaction system to enable rational yield prediction in transglycosylation reactions via principles of thermodynamic control.<br>